A major point of this episode is that when the parasites are killed, they vanish from history and so the past is altered - things like medical scans appear as if the parasites had never existed. But that would mean that the memories people had of those medical scans would also be re-written, so T'Pol and Phlox would never know anything had happened. In fact, Phlox could never even know his treatment had worked at all!

In fact an interesting thing should have happened here. Phlox picked a parasite to test his treatment on. When it worked and the parasite was erased from history, in the new reality Phlox would have picked another parasite instead. So that one would then vanish from history and make another new timeline. In this one Phlox would pick yet another parasite... and so on. The upshot is, as soon as Phlox did his first treatment ALL the parasites should have vanished and the episode would be over! But if the parasites had never been there, why would Phlox invent the treatment in the first place... time travel makes no sense at all, does it?

Great Moment :

Earth blowing up - the most spectacular planet destruction I've ever seen on film, bar none. Also the last battle was amazing, including the bridge being blown off Enterprise.

Body Count :

The whole planet Earth and most of the Human race! We also see several ships destroyed, including Enterprise.

Factoid :

Ceti Alpha V, the planet where the last Humans settled, is the same planet Kirk dumped Khan on a hundred or so years later. Amusing to think that even if the Xindi had not found them, things would have gotten much worse for the Humans when Ceti Alpha VI exploded later on!

We see another TNG species for the first time in this episode - the Yridians.

Plotline

Archer is infected by neural parasites which destroy his ability to create long term memories. Waking each day he must be told everything that has happened since he was infected - including the story of the destruction of Earth and virtual annhilation of Humanity.